DELTOID LIGAMENT FORCES AFTER TIBIALIS POSTERIOR TENDON-RUPTURE - EFFECTS OF TRIPLE ARTHRODESIS AND CALCANEAL DISPLACEMENT OSTEOTOMIES

Deltoid ligament forces were studied after observing deltoid ligament insufficiency in several post-triple arthrodesis patients. Six fresh-f rozen, below-knee amputation specimens were axially loaded. The result s demonstrate that a properly positioned triple arthrodesis produced d eltoid ligament forces that were similar to those seen with an intact tibialis posterior tendon. A triple arthrodesis in combination with a lateral displacement calcaneal osteotomy produced deltoid ligament for ces that were 76% greater than those seen with the intact tibialis pos terior tendon (P<.05). A triple arthrodesis in combination with a medi al displacement calcaneal osteotomy produced deltoid ligament forces t hat were 56% less than those seen with the lateral displacement calcan eal osteotomy (P <.01). Patients with longstanding ruptures of the tib ialis posterior tendon and associated peritalar subluxation/dislocatio n may have less than optimal clinical results after triple arthrodesis , unless the hindfoot can be properly reduced, due to persistent eleva ted forces in the deltoid ligament and resulting ligament laxity. This study suggests that a medial displacement calcaneal osteotomy in comb ination with a triple arthrodesis may be a viable treatment when the h indfoot cannot be positioned properly.